Kaeser had responded to earlier criticism from Schulz in an open letter published by the Handelsblatt newspaper on Thursday, saying his use of “populist and aggressive slogans” could aid the company’s competition.

Schulz, whose party agreed on Friday to enter talks with Chancellor Angela Merkel’s conservatives about renewing its outgoing coalition government, said he had read Kaeser’s letter but did not plan to respond in kind.

“I’m not going to write an open letter, but I am going to repeat what I said: A company that reports profits of 6.3 billion euros and then fires 6,900 people is acting anti-socially and not socially,” he told the SPD’s youth wing at a conference in the western city of Saarbruecken.

Siemens last week announced it would cut close to 2 percent of its global workforce, with about half the cuts to be made in Germany.

The plans have triggered protests by thousands of workers at various Siemens sites in Germany.

Schulz previously has suggested the German government could respond to the job cuts by scaling back orders for Siemens, a big government contractor.

In his letter, Kaeser shot back that Siemens also pays 20 billion euros in taxes and social security contributions, according to Handelsblatt.

Critics say Siemens’ job cuts will increase unemployment in economically challenged parts of former East Germany, and could bolster support for the far-right Alternative for Germany (AfD).

Lothar de Maiziere, the last prime minister of East Germany and former deputy leader of Chancellor Angela Merkel’s conservatives, told the RND newspaper chain that Siemens was motivated purely by “despicable profits” and had no interest in its social responsibilities.

He said the company was taking advantage of the political crisis in Germany and the state of Saxony, where the AfD overtook the CDU to become the strongest party.

“Frustration leads to extremism and further migration (out of the region). So no one should be surprised that the AfD is making such strong gains in the east. It is benefiting from the dissatisfaction and the fears of the people.” (Reporting by Andrea Shalal; Editing by Lisa Shumaker)